1. Field of the Invention
The present invention relates to a valve driving apparatus of an internal combustion engine and, more particularly to a valve driving apparatus for driving an intake or an exhaust valve by using an electromagnetic force generated when a predetermined electric power is supplied to an electromagnetic coil.
2. Description of the Related Art
A valve driving apparatus is known in the art which drives an intake valve or an exhaust valve of an internal combustion engine by using an electromagnetic force generated by an electromagnetic coil. Japanese Laid-Open Patent Application No. 2-181006 discloses an example of such a valve driving apparatus. Such a valve driving apparatus eliminates a valve driving mechanism such as a camming mechanism. Additionally, since an ideal timing of opening and closing of the valves can be easily provided based on an operational condition of the internal combustion engine, output characteristics and specific fuel consumption of the internal combustion engine can be improved.
The above-mentioned conventional valve driving apparatus generates an electromagnetic force by supplying a predetermined current to an electromagnetic coil. A valve body is moved toward an open position or a closed position by the electromagnetic force. If the current is supplied for the purpose of merely moving the valve body, the valve body may be strongly moved toward the open position or the closed position. This may result in generation of noise and reduces service life of the valve body. However, in the conventional valve driving apparatus, the current supplied to the electromagnetic coil is controlled without any consideration with respect to a seating characteristics of the valve body. Accordingly, the conventional valve driving apparatus does not always provide a desired characteristics with respect to a low noise operation and a long service life of the valve body.